One of the ideas that fell out of Steven Moffat's purposefully vague description of this year's Christmas Special as "like a compilation of every Christmas movie" was the joking suggestion it would be like The Great Escape because it was famously on TV just about annually in the 70s and 80s.
So that got me thinking of what a Doctor Who version of The Great Escape would look like. Alien prison, maybe a whole planet or a satellite in space. Robotic guards and corrupt humanoid warders. Prisoners from various species and possibly time periods having to work together to get free. And more time on the escape than the plan, of course. And if anybody does the motorcycle jump, it would be the Doctor.
But last night I had a different idea. Start in medias res, in a Porridge-style underfunded Victorian-built prison in 1960s Britain, with its beaten-down cons, its fixers, hard men (the version in my head features big bald character actor Steve Speirs as a surprisingly sensitive soul) and bosses (maybe Kevin McNally, since he was in The Twin Dilemma and deserves better)... and we see a van full of new prisoners being brought in. And the third one out is the Doctor.
Why is he there? A place like this would be impossible for him not to escape from. So why is he in here?